$ { {1} \times \left[\begin{array}{rrr}{1} & {2} & {1} \\ {0} & {4} & {-2}\end{array}\right] = {?} } $
Solution: To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rrr}{1}\times{1} & {1}\times{2} & {1}\times{1} \\ {1}\times{0} & {1}\times{4} & {1}\times{-2}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rrr}{1} & {2} & {1} \\ {0} & {4} & {-2}\end{array}\right]}$